diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ConstraintsProcessing.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ConstraintsProcessing.kt
index b2583767..83ba62d2 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ConstraintsProcessing.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ConstraintsProcessing.kt
@@ -56,6 +56,13 @@ internal class ConstraintsProcessing(
 
     fun getStateCleaner(): ProgramStateCleaner = ProgramStateCleaner()
 
+    fun engage(controller: Controller) {
+        logicalState.setController(controller)
+    }
+
+    fun disengage(controller: Controller) {
+        logicalState.clearController(controller)
+    }
 
     fun activateContinue(controller: Controller, activeOcc: Occurrence, parent: MatchJournal.MatchChunk): FeedbackStatus {
         assert(activeOcc.stored)
diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ControllerImpl.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ControllerImpl.kt
index 1b7e6abc..e7378ab8 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ControllerImpl.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/ControllerImpl.kt
@@ -36,6 +36,14 @@ internal class ControllerImpl (
     val profiler: Profiler? = null) : Controller, IncrSpecHolder
 {
 
+    init {
+        processing.engage(this)
+    }
+
+    fun shutDown() {
+        processing.disengage(this)
+    }
+
     /** For tests only */
     override fun storeView(): StoreView = processing.storeView()
 
@@ -361,6 +369,5 @@ fun createController(
         trace,
         profiler
     )
-    logicalState.init(controller)
     return controller
 }
diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt
index 54b17543..74361d7b 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/EvaluationSessionImpl.kt
@@ -111,7 +111,6 @@ internal class EvaluationSessionImpl private constructor (
             processing.setStrategy(processingStrategy)
 
             val controller = ControllerImpl(supervisor, processing, incrementality, trace, profiler)
-            logicalState.init(controller)
 
             return SessionParts(program.preambleInfo(), ruleIndex, journal, logicalState, dispatchingFront, controller, processing, processingStrategy)
         }
@@ -121,18 +120,20 @@ internal class EvaluationSessionImpl private constructor (
                 journal.view(),
                 ruleIndex.toRules(),
                 emptyFrontState(),
-                logicalState.clear(),
+                logicalState,
                 ruleIndex
             )
         }
 
         override fun runSession(session: SessionParts, main: Constraint): EvaluationResult = with(session) {
             val status = run(main)
+            controller.shutDown()
             val newToken = endSession(session)
             return EvaluationResultImpl(newToken, status, strategy.invalidatedFeedback())
         }
 
         private fun SessionParts.run(main: Constraint): FeedbackStatus = strategy.run(processing, controller, main)
+
     }
 
     open inner class IncrementalProcessingSession(): DefaultProcessingSession() {
@@ -151,7 +152,6 @@ internal class EvaluationSessionImpl private constructor (
             processing.setStrategy(processingStrategy)
 
             val controller = ControllerImpl(supervisor, processing, incrementality, trace, profiler)
-            logicalState.init(controller)
 
             return SessionParts(program.preambleInfo(), ruleIndex, journal, logicalState, front, controller, processing, processingStrategy)
         }
@@ -161,7 +161,7 @@ internal class EvaluationSessionImpl private constructor (
             processing.resetStore() // clear observers
             // todo: need clearing occurrenceContractObservers? (MPSCR-66)
             val principalState = dispatchingFront.sessionState()
-            return SessionTokenImpl(histView, ruleIndex.toRules(), principalState, logicalState.clear(), ruleIndex)
+            return SessionTokenImpl(histView, ruleIndex.toRules(), principalState, logicalState, ruleIndex)
         }
 
         /**
@@ -192,7 +192,6 @@ internal class EvaluationSessionImpl private constructor (
             processing.setStrategy(processingStrategy)
 
             val controller = ControllerImpl(supervisor, processing, incrementality, trace, profiler)
-            logicalState.init(controller)
 
             this.tkn = tkn
             return SessionParts(program.preambleInfo(), ruleIndex, journal, logicalState, front, controller, processing, processingStrategy)
@@ -214,7 +213,7 @@ internal class EvaluationSessionImpl private constructor (
                 val rules = ruleIndex.toRules().filter(preambleInfo::inPreamble)
 
                 logicalState.reset()
-                tkn = SessionTokenImpl(histView, rules, principalState, logicalState.clear(), ruleIndex)
+                tkn = SessionTokenImpl(histView, rules, principalState, logicalState, ruleIndex)
             }
             return tkn!!
         }
diff --git a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/LogicalState.kt b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/LogicalState.kt
index 8b5f9ed2..3cb026c0 100644
--- a/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/LogicalState.kt
+++ b/reactor/Core/src/jetbrains/mps/logic/reactor/core/internal/LogicalState.kt
@@ -50,13 +50,13 @@ class LogicalState : LogicalStateObservable, LogicalObserver
         stateFrames.push(LogicalStateFrame())
     }
 
-    fun init(controller: Controller) {
+    internal fun setController(controller: Controller) {
         assert(this.controller === null)
         this.controller = controller
     }
 
-    fun clear() : LogicalState {
-        assert(this.controller !== null)
+    internal fun clearController(currController: Controller) : LogicalState {
+        assert(this.controller == currController)
         this.controller = null
         return this
     }